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Low level of Lake Superior raises concern and costs

Jim Sharrow stands next to a boat dock, with posts sunken into the rocks. They stick well above the frozen water surface. It's dramatic evidence of the low lake level.

"This post was six inches submerged in water. That was in 2006, over most of the summer," Sharrow says. "This summer the actual water level was about eight to 10 inches below that, typically. And right now it has come down so far that we're about two feet out of the water, and there's a whole shoreline slope that's developed with this receding water line."

It's more than an inconvenience. It's a costly problem for the people who ship grain and taconite in ships.

Jim SharrowMPR Photo/Bob Kelleher

Sharrow works for the Duluth Seaway Port Authority. He says the ships that call on the port have to load light to keep from hitting bottom in harbors and shipping channels.

An oceangoing ship might have to cut 135 to 140 tons of grain for each inch it has to load light. A 1,000-foot lake freighter can lose 275 tons of taconite pellets or coal for every inch it has to cut.
"And that doesn't sound like very much, but if you multiply that by a difference between of water levels now versus several years ago when they were at closer to high water levels, we're at more than 24 inches of difference," Sharrow says. "On a 1,000 footer you're talking about 6,000 tons, which is nearly 10 percent of their capacity."

Sharrow says that can represent a ship's total profit.

It's also a costly problem for the companies that load ships. Mike Kylmala manages Duluth's ADP grain elevator, which loads mostly oceangoing ships. This year, they've had to dig a much deeper channel next to their ship dock, dredging about 3,000 cubic yards at a considerable expense.

Ore shipMPR Photo

"It is an ongoing problem," Kylmala says. "And hopefully the lake quits going down so much, or we're going to need substantial snow this winter, and probably a good wet spring to get it to come back."

And Kylmala worries about next year.

"You get in a situation where you just can't keep dredging. Your sheet piling, like ours, I think averages around 30 feet. So you can't start digging down too much and undermining the sheet piling. We're getting to, I suppose, almost our maximum now."

The lake is a victim of the weather, and the weather has been warm and dry. The Duluth region is officially in extreme drought. As of late December, Duluth's rainfall is seven inches below normal for the year.

But there's something else. The lake itself is warming even more quickly than the surrounding air, according to Steve Colman.

"The water temperatures are rising dramatically, which is not unexpected, since the regional air temperatures, just like the global air temperatures, have gone up measurably," says Colman, who directs the Large Lakes Observatory at the University of Minnesota-Duluth.

He says the region's air temperatures are running about one-and-a-half degrees Fahrenheit higher than in 1980.

"The other thing that really made this much more compelling is that the average water temperatures have increased two to three times that much."

The cause appears to be less winter ice on Lake Superior. And that can result in less water.

"If the lake is less ice-covered, there's more potential for evaporation, even in the winter, which tends to suppress lake level," Colman says. "And the other observation that we have, is that along with the temperature increase, the wind speeds have increased."

Which, he says, will also promote evaporation.

The long-term data may be troubling, but people with the shipping industry, like Jim Sharrow, are hoping for a turnaround in the short term.

"And who's to say? We may have above-average rainfall next year and all the water will come back," Sharrow says. "Who knows?"

While the lake stands at an all-time low level, the record won't be set until record keepers calculate a low average level at the end of the month.